Find the sum S of the infinite series Σk=1∞ 6·(−1/4)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 6r = −1/4k₀ = 1
S =
2.Easy
Find the sum S9 of the first 9 terms of the geometric sequence 5, 2.5, 1.25, …
a₁ = 5r = 0.5n = 9
S9 =
3.Medium
Apply the ratio test to Σk=1∞ 3ᵏ·k!/kᵏ. Find L = lim |ak+1/ak|.
ak = 3ᵏ·k!/kᵏ
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (3/5)ᵏB: Σ 1/k²C: Σ k/(k + 7)D: Σ 1/(k² + 6)
- 1A: Σ (3/5)ᵏ
- 2B: Σ 1/k²
- 3C: Σ k/(k + 7)
- 4D: Σ 1/(k² + 6)
5.Hard
Recognise the series and find its sum: S = Σk=0∞ 1.5ᵏ/k!.
ak = 1.5ᵏ/k!
S =
6.Hard
Recognise the series and find its sum: S = Σk=1∞ k·0.25ᵏ.
ak = k·0.25ᵏ
S =
Answer key
- 1. S = −1.2
- 2. S9 = 9.98
- 3. L = 1.104
- 4. C: Σ k/(k + 7)
- 5. S = 4.482
- 6. S = 0.4444
Full step-by-step solutions: practise this topic on examproblems.com.